A mountain pass is a long time in the Tour de France. At the foot of Chamrousse on Friday, the Movistar team of Alejandro Valverde felt sufficiently optimistic to force the pace in a bid to unsettle an increasingly isolated Vincenzo Nibali (Astana).

By the summit of the climb, some 18 sun-beaten kilometres later, Valverde was already riding simply to defend the second step of the podium in Paris, while Nibali was soloing to his third stage victory at this year’s Tour and adding another 50 seconds to his overall buffer for good measure.

If the Tour’s belated entry into the high mountains was supposed to provide the true test of Nibali’s credentials, then he more than passed muster. Instead, it was his rivals who suffered on this first day in the Alps. While Thibaut Pinot (FDJ.fr) made some waves, Valverde could only tread water and Richie Porte (Sky) floundered altogether, losing 8:48 and slipping from second to 16th on general classification.

"I’m happy because I gained important seconds for the overall on Valverde and Porte had a crisis," Nibali said afterwards. "That was already very important, and then winning the stage on a long, interminable climb with that high temperature, made me very happy. Maybe winning in the yellow jersey makes this more significant than the other stage wins."

Nibali’s victory came in three parts. With 12 kilometres remaining, he responded coolly to the forcing of Pinot and Valverde, before launching a vicious attack of his own 6.5 kilometres from the top. That acceleration brought Nibali across to earlier escapees Leopold König and Rafal Majka, and after recovering from his first effort, he eased away from them just shy of the 3km to go banner.

"I saw that Richie Porte was being dropped, and after that my objective was to gain important seconds on people like Valverde," Nibali said. "I made my acceleration to try and catch up to the leaders and then I looked for a bit of collaboration from them because it was a long way to the finish and there’s another tough day tomorrow, too. In the end, I could sense that Valverde was coming closer with Thibaut Pinot, so I tried to force the pace again in the finale."

Astana showing wear and tear

Although Nibali has scarcely put a pedal stroke askew since the Tour began in Leeds, his Astana team showed some signs of wear on the race’s first day in the Alps. Michele Scarponi fell away on the penultimate climb, the Palaquit, Jakob Fuglsang crashed on the descent and Lieuwe Westra was distanced early on the final climb. When Tanel Kangert swung off after his mammoth turn, Nibali was left without support for the final 12 kilometres, but he said that he was not concerned.

"Today they were very strong at the start and the most important guys for the mountains, like Kangert and Westra, stayed up there with me in the end," he said. "Unfortunately Fuglsang crashed, but I hope he won’t have too many problems and will be able to recover. But I’m pretty tranquillo about the team."

Nibali is now 3:37 clear of Valverde, with Romain Bardet (Ag2r-La Mondiale) 4:43 down in third, and Thibaut Pinot was to the point in his appraisal of the overall picture afterwards – "There’s Nibali and then there’s everyone else." Indeed, such is the Italian’s dominance that many of his overall rivals already seem resigned to marking one another rather than attempting to match his accelerations.

"Today I think that there were attacks aimed at me too," Nibali protested. "Movistar set a very high tempo at the bottom of the last climb, and I was thinking to myself that the climb was still very long. But little by little, I saw that the group was breaking up and reduced and that was good for me, as I could control the guys in contention for the classification."

When Nibali was reminded that his victory had fallen on the 100th anniversary of Gino Bartali’s birth, he pointed out that July 18 marks another, tragic anniversary. Nibali was just ten years old when Fabio Casartelli was killed in a crash on the Col de Portet d’Aspet in the 1995 Tour, a stage he had watched on television at home in Messina.

"Today is the anniversary of Casartelli’s death, too. I was only a child when it happened but I remember the event very clearly and winning on a day like today was very important for me," Nibali said.